Title says it all. Are there any mods that might help lower system requirements?

Skyrim Performance Plus: http://skyrim.nexusmods.com/mods/6387 - Reduces the texture resolution of some of the more intensive particle effect animations (snow, rain, leaves.)

HiAlgoBoost: http://skyrim.nexusmods.com/mods/15123 - Mostly helps smooth framerates while moving the character. Does so by lowering the resolution dynamically (but since you're moving it's harder to notice the drop.) Helps some people more than others.

Shadow Remover: http://skyrim.nexusmods.com/mods/16464 - Not really a mod, just ini tweaks. Disables shadows while preserving lighting effects. Shadows are a huge performance drain, so this can help a lot.

Not sure how much these'll lower requirements, but they should help performance at least.

edit: Skyrim Mods Complex Optimizer: http://skyrim.nexusmods.com/mods/13529 - This modifies the mods you use by resaving textures in more efficient file formats and better compressing .BSAs. Also has some .nif model optimization, but that can lead to problems with certain models. The main benefit is shrinking the size of your textures by better selecting which .dds format they're saved in. The uptake of smaller textures is that you'll need less VRAM to load that texture into memory, which really adds up if you use a lot of texture heavy mods.

Bethesda Hi-Res DLC Optimized: http://skyrim.nexusmods.com/mods/9080 - Modifies the Hi-Resolution Texture DLC by downsizing textures that don't particularly merit the 2048 size the DLC increased everything to. Will effect quality over the default DLC, but shouldn't be particularly noticable. You can run SMCO over these files for additional savings.